I can throw in a couple that I think are new.
Mandatory SpoilersThings that drastically affect gameplay that you have to figure out either through trial and error, or reading a guide. Revenge of the Titans is the worst, but I sort-of ruined a builder world in Terraria by activating hardmode because I had avoided spoilers for it. Now it's all overrun. Also, a few missions in Heroes of Might and Magic V I wouldn't have figured out on my own easily without a guide. And that leads me to:
Repetition via RNGAgain, Heroes V comes to mind. Have a build you want to try for your hero? Hope the dice say you can. Got to mission 3 of a campaign without destructive magic? Re-roll and pray, because you must have it for X or Y. As a sub-set, having loot that is both rare and drops from a rarely occurring enemy. 1 in 100,000 chance to get a Golden MacGuffin from the only warbling Mookasaurus in the game that takes 15 minutes to get to? TitanQuest, and Borderlands (1) I'm looking at you.
Also:
"Bragging Rights" rewards.It can be something pointless, like a king's crown and cape outfit, or something awesome like the +5 Nuclear Sword of From Orbit... if I have to kill the ultimate bonus boss to get it (and hence, kill what I would have needed to use it ON) it's useless.
Last-act Party MemberAKA
Eleventh Hour Ranger. Legion in Mass Effect 2, for instance. Want the best ending? get him absolutely last, do his two missions, endgame. Worst example would be Himi from Golden Sun: Dark Dawn, who actually
asks who the villain is during the last fight. Just... wow.